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array_diff_assoc

(PHP 4 >= 4.3.0, PHP 5)

array_diff_assoc -- 带索引检查计算数组的差集

说明

array array_diff_assoc ( array array1, array array2 [, array ...] )

array_diff_assoc() 返回一个数组，该数组包括了所有在 array1 中但是不在任何其它参数数组中的值。注意和 array_diff() 不同的是键名也用于比较。

例 1. array_diff_assoc() 例子

<?php
$array1 = array ("a" => "green", "b" => "brown", "c" => "blue", "red");
$array2 = array ("a" => "green", "yellow", "red");
$result = array_diff_assoc($array1, $array2);
?>

上例将输出：

Array
(
    [b] => brown
    [c] => blue
    [0] => red
)

上面的例子中可以看到键值对 "a" => "green" 在两个数组中都有，因此不在本函数的输出中。与此不同，键值对 0 => "red" 出现在输出中是因为第二个参数中的 "red" 的键名是 1。

键值对 key => value 中的两个值仅在 (string) $elem1 === (string) $elem2 时被认为相等。也就是说使用了严格检查，字符串的表达必须相同。

注意: 注意本函数只检查了多维数组中的一维。当然可以用 array_diff_assoc($array1[0], $array2[0]); 检查更深的维度。

参见 array_diff()，array_intersect() 和 array_intersect_assoc()。


add a note add a note User Contributed Notes
cedric at daneel dot net
21-May-2007 01:01
To diff between n-dimensional array, juste use this :

function array_diff_values($tab1, $tab2)
   {
   $result = array();
   foreach($tab1 as $values) if(! in_array($values, $tab2)) $result[] = $values;
   return $result;
   }
contact at pascalopitz dot com
11-Apr-2007 11:14
The direction of the arguments does actually make a difference:

<?
$a = array(
   'x' => 'x',
   'y' => 'y',
   'z' => 'z',
   't' => 't',
);

$b = array(
   'x' => 'x',
   'y' => 'y',
   'z' => 'z',
   't' => 't',
   'g' => 'g',
);

print_r(array_diff_assoc($a, $b));
print_r(array_diff_assoc($b, $a));
?>

echoes:

Array
(
)
Array
(
   [g] => g
)
chinello at gmail dot com
19-Mar-2007 06:33
A small modification for array_diff_assoc_recursive from 'sc1n at yahoo dot com' , to not display any notices if a key don't exist and if error_reporting is set to E_ALL:
<?php
function array_diff_assoc_recursive($array1, $array2)
{
   foreach($array1 as $key => $value)
   {
       if(is_array($value))
       {
             if(!isset($array2[$key]))
             {
                 $difference[$key] = $value;
             }
             elseif(!is_array($array2[$key]))
             {
                 $difference[$key] = $value;
             }
             else
             {
                 $new_diff = array_diff_assoc_recursive($value, $array2[$key]);
                 if($new_diff != FALSE)
                 {
                       $difference[$key] = $new_diff;
                 }
             }
         }
         elseif(!isset($array2[$key]) || $array2[$key] != $value)
         {
             $difference[$key] = $value;
         }
   }
   return !isset($difference) ? 0 : $difference;
}
?>
Alexander Podgorny
30-May-2006 09:30
NOTE: the diff_array also removes all the duplicate values that match to the values in the second array:

<?
   $array1 = array("a","b","c","a","a");
   $array2 = array("a");

   $diff = array_diff($array1,$array2);

   // yields: array("b","c") the duplicate "a" values are removed
?>
benjamin at moonfactory dot co dot jp
12-Jan-2005 05:56
Hi all,
For php versions < 4.3...

<?php
/**
 * array_diff_assoc for version < 4.3
 **/
if (!function_exists('array_diff_assoc'))
{
   function array_diff_assoc($a1, $a2)
   {
       foreach($a1 as $key => $value)
       {
           if(isset($a2[$key]))
           {
               if((string) $value !== (string) $a2[$key])
               {
                     $r[$key] = $value;
               }
           }else
           {
               $r[$key] = $value;
           }
       }
       return $r ;
   }
}

Hope there's no bug,
cheers
?>
aidan at php dot net
09-Jun-2004 01:34
This functionality is now implemented in the PEAR package PHP_Compat.

More information about using this function without upgrading your version of PHP can be found on the below link:

http://pear.php.net/package/PHP_Compat
Michael Johnson
26-Oct-2003 07:20
[jochem at iamjochem dawt com]
Here is a slightly enhanced version of Micheal Johnsons function.
This version accepts arguments in the same way as
array_diff_assoc (i.e. you can pass as many arrays as you want - any
arguments that are not arrays are ignored). If the first argument is not an array you automatically get empty array back:

The point of the function is to return all values in the first array
whose keys (only keys are checked!) are not present in any subsequently passed arrays.

[original post]
array_diff_assoc() requires that both the key and the value pairs match. To match based on keys only, try this function.

<?php
function array_diff_keys()
{
   $args = func_get_args();

   $res = $args[0];
   if(!is_array($res)) {
       return array();
   }

   for($i=1;$i<count($args);$i++) {
       if(!is_array($args[$i])) {
           continue;
       }
       foreach ($args[$i] as $key => $data) {
           unset($res[$key]);
       }
   }
   return $res;
}

// Example
$a = array('a' => '1', 'b' => '2', 'c' => '3');
$b = array('a' => '2', 'b' => '2', 'e' => '4');

// Yields array('a' => '1', 'c' => '3')
// Note that the 'a' index is not removed (as one might expect)
$c = array_diff_assoc($a, $b);

// Yields array('c' => '3')
$d = array_diff_keys($a, $b);
?>
sc1n at yahoo dot com
11-Jul-2003 07:10
[anders dot carlsson at mds dot mdh dot se]
The user contributed array_diff_assoc_recursive function is good except for the original array_diff_assoc always (?) returns an array.

Therefore I propose that $difference is initially set to an empty array (and the array is always returned), and the comparison against FALSE is replaced by count($new_diff). At least that's the modifications I made to run it they way my code expects.

[original post]
The following will recursively do an array_diff_assoc, which will calculate differences on a multi-dimensional level.  (Forgive me if the braces do not line up, the note script did not like my tabs, and gave me trouble on some spaces.)

<?php
function array_diff_assoc_recursive($array1, $array2)
{
     foreach($array1 as $key => $value)
     {
         if(is_array($value))
         {
               if(!is_array($array2[$key]))
               {
                   $difference[$key] = $value;
               }
               else
               {
                   $new_diff = array_diff_assoc_recursive($value, $array2[$key]);
                   if($new_diff != FALSE)
                   {
                         $difference[$key] = $new_diff;
                   }                               
               }
           }
           elseif(!isset($array2[$key]) || $array2[$key] != $value)
           {
               $difference[$key] = $value;
           }
     }
     return !isset($difference) ? 0 : $difference;
}
?>
carl at thep dot lu dot se
09-May-2003 09:55
To unset elements in an array if you know the keys but not the values, you can do:

<?php
$a = array("foo", "bar", "baz", "quux");
$b = array(1, 3); // Elements to get rid of

foreach($b as $e)
  unset($a[$e]);
?>

Of course this makes most sense if $b has many elements or is dynamically generated.
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